The present invention is directed to container and closure packages in which the container is extrusion blow molded, and more particularly to a closure for sealing engagement with a trimmed surface at the finish of an extrusion blow molded plastic container.
Extrusion blow molded (EBM) plastic containers are conventionally formed by extruding a tube of plastic material, capturing the tube between opposing mold halves, and forming the tube against the internal surfaces of the mold halves by injection or blowing with air under pressure. See, for example, U.S. Pat. Nos. 4,523,904 and 5,851,479. Employing conventional technology, there can be a mismatch between adjacent edges of the mold halves on the order of as much as 0.010 to 0.015 inch, leading to formation of a step-like structure on the outer surface of the container along the line(s) of mold mismatch. When a closure is applied to the blow-molded finish of such a container, sealing engagement between the closure and the container surface can be less than optimum at the area of mold mismatch, reducing shelf life of the product within the container.
It is a general object of the present invention to provide a container and closure package, and a method of making such a package, in which the closure is constructed for sealing engagement with a trimmed area of the container finish, as distinguished from an external surface area of the container finish, so that mold mismatch during the container forming operation will not reduce the effectiveness of such sealing engagement, and shelf life of the package will be improved. Another object of the present invention is to provide a closure constructed for sealing engagement with a trimmed area of an extrusion blow molded container finish.
A method of making a package in accordance with one aspect of the present invention includes the steps of blow molding a hollow plastic container, including blow molding a finish and a moil or dome that extends from the finish, and trimming the moil or dome from the container finish so as to leave a conical flange extending inwardly and upwardly from the finish terminating in a smooth trimmed surface. A closure is provided having a base wall and a peripheral skirt. A liner is secured to the base wall within the skirt, and has a radially outwardly facing sealing surface spaced from and opposed to the skirt. The closure is secured to the container finish in such a way that the conical flange of the container extending from the finish is deformed radially inwardly and axially downwardly by a peripheral portion of the liner so as to bring the trimmed surface of the container flange into abutment sealing engagement with the sealing surface of the liner. In various embodiments of the invention, the radially outwardly facing sealing surface on the liner is conical, convex, or formed by a hooked protrusion that extends axially from the liner. Sealing engagement between the closure and the container is thus obtained at least in part between the closure liner and a trimmed surface of the container finish.
A container and closure package in accordance with another aspect of the present invention includes a closure having a base wall and a peripheral skirt with internal means, such as an internal thread or bead, for securing the closure to a container. A liner is secured to the base wall of the closure within the skirt. The liner has a radially outwardly oriented sealing surface spaced from and opposed to the skirt, and a liner periphery extending from the sealing surface toward the skirt. A container has a finish with external means, such as an external thread or bead, for securement of the closure, and an axially outwardly and radially inwardly extending flange flexibly coupled to the finish and terminating in a smooth sealing surface. The flange is deformed inwardly and downwardly by the liner periphery as the closure is secured to the container finish so as to drive the sealing surface on the flange into opposed sealing engagement with the sealing surface on the liner.
A closure in accordance with another aspect of the present invention includes a plastic shell having a base wall and a peripheral skirt with internal means, such as an internal thread or bead, for securing the closure to the finish of a container. A flexible resilient plastic liner is secured to the base wall of the closure within the skirt, such as by being compression molded in situ against the base wall, or less preferably by being formed separately and secured to the base wall of the closure. The liner has a radially outwardly oriented sealing surface spaced from and opposed to the closure skirt for opposed abutment sealing engagement with a trimmed surface on the container finish. The liner has a peripheral portion between the sealing surface and the closure skirt for slidable camming engagement with a container finish to deform the container finish axially and radially into abutment sealing engagement with the sealing surface on the liner.